Tamping plug

ABSTRACT

The invention provides for a plug for use in blasting holes, the plug consisting of substantially rectangular section striplike material formed into a cone-shaped spiral member in which the convolutions overlap one another and having their larger faces diverging in the direction of the small end of the member.

United States Patent Inventor Vernon Jan Botes Johannesburg, SouthAfrica Appl. No. 787,161 Filed Dec. 26, 1968 Patented Sept. 28, 1971Assignee Dunaplug (Proprietary) Limited Pietersburg Transvaak Province,South Africa Priority Dec. 27, 1967 South Africa 671-7731 TAMPING PLUG 710 Claims, 10 Drawing Figs.

US. Cl 102/30 Int. Cl F42d 1/08 Field of Search 102/26, 30;

[56] References Cited UNITED STATES PATENTS 2,403,386 7/1946 Lubelsky etal 102/30 2,553,757 5/1951 Evans 156/195 X 3,081,705 3/1963 Warnken156/195 X Primary Examiner-Verlin R. Pendegrass Attorney- Karl W. FlocksABSTRACT: *The invention provides for a plug for use in blasting holes,the plug consisting of substantially rectangular section striplikematerial formed into a cone-shaped spiral member in which theeonvolutions overlap one another and having their larger faces divergingin the direction of the small end of the member.

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TAMPING PLUG BACKGROUND OF THE INVENTION This invention relates to animproved plug and more par ticularly a tamping plug for bored blastholes.

According to the invention a tamping tubular plug member is providedhaving a wide end and a small end and comprising a helically wound stripof material presenting a pair of opposed wide faces, the helically woundstrip material providing overlapping convolutions of progressivelysmaller size and which convolutions are arranged with both the widerfaces of the strip material convergent toward the wide end of the memberand with smaller convolutions extending from the larger convolutions,within which they are disposed, in the direction of the small end of themember whereby, on application of a force in a substantially axialdirection on the small end of the member and toward the wide end of themember, the wide faces of the helically wound strip slide and engagewedgingly on one another and cause radial expansion of the convolutionsfor the convolution at the wide end of the member to be tightly engagedonto walls of a hole in which the member is located.

When the strip material has been wound or shaped and formed to presentthe tapering tubular plug member the outer face of the outermostconvolution is preferably of substantially constant radius on the axisof the member to form a substantially true cylinder which is surmountedby a generally conical surface of substantially helically ribbedappearance presented by exposed portions of the overlapped convolutionsof the helically wound strip material. The outwardly directed surface ofthe outer appearance. The The outwardly directed surface of theoutermost convolution may be provided with ribs or other rougheningformations to increase frictional engagement on the walls of the hole inwhich the plug member is inserted.

To insert the plug member according to the invention, the wide end isheld and the small end forced into the hole with the aid of a rod or barto the required depth and whereby the tapering tubular member isextended in length and reduced in respect of its width. The held wideend or outer end of the strip material is then slowly allowed to bemoved inwardly when the length is reduced and the width increased. Saidwide end may be subsequently forced further into the hole and, due

becomes firmly held in the hole. When subjected to pressure on the smallend, the lateral expanding action is increased due to the wcdging actionof the overlapping convolutions and as a result of which the plug memberbecomes firmly held in the hole. Such wcdging action may be increased byproviding the strip material with the substantially wedge-shaped crosssection.

If required the transverse end portion at the narrow end of the stripmaterial wound spirally and outwardly overlappingly to truncatedcone-shape, may be twisted through an angle of approximately 90 topresent a larger face disposed across the narrow end of the member.

The strip material should be a suitable nonferrous material butadvantageously comprises a synthetic resinous or plastic material.

For the invention to be readily understood, reference will now be madeto the accompanying drawings in which:

FIG. l is a pictorial view ofa tamping plug member according to theinvention;

FIG. 2 is a cross section of a tamping plug member according to theinvention, drawn to a larger scale;

FIG. 3 is a cross section of a tamping plug member shown in positionwithin a hole;

FIG. 4 is a view similar to FIG. 3 shown in a larger diameter hole; and

FIG. 5 to are cross sections of modified forms of plug membersconstructed according to the invention.

Referring to the drawings reference numeral 10 denotes a truncatedcone-shaped plug member formed by helical conto the recoiling action ofthe coils, expands transversely and volutions of strip material 12. Theconvolutions are outwardly overlapping. The top end 14 of the strip istwisted through an angle of approximately as at 16, to be disposedradially and substantially diametrically across the small end 18 of thetruncated cone 10. The tip end 14 is provided with a hole 20 which isdisposed coaxially with the axis of the truncated cone 10. However, saidtip end 14 is not essential and need not be provided.

The strip material [2 is preferably of tapering cross-sectional shape asis clearly shown in FIG. 2.

The strip material 12 is preferably of a suitable synthetic resinous orthemo plastic material.

The small end convolution according to the modification shown in FIG. 5provides a thicker portion 22 of which the outer surface forms atruncated cone converging towards the wide end of the truncatedconically shaped plug member. Said portion 22 may be provided on itssmaller end with a lip adapted to form a tubular region 24 and forms anaxial passage 26 through which a fuse may be passed.

The small end convolution 22.1 according to the form of plug membershown in FIG. 6 may be provided with an outwardly flared lip 28 topresent an increased projected area on the small end of the plug member.Said lip 28 may be in the form of wings moulded integrally with the topconvolution forming portion of the strip material. Said lip 28 may beprovided with radial slits if required.

The aforesaid small end convolution of the plug member in the forms ofthe invention shown in FIGS. 5 and 6 may be formed as a solid annulus towhich one end of the strip material is attached.

As it may be necessary in certain instances to remove a plug member froma hole in which it has been placed, a ridge 30 or a groove or recess 32may be provided on or in the inside face of one of the largerconvolutions as is shown in FIGS. 7 and 8. Preferably the large endconvolution is provided with such ridge 30 or groove 32 for engagementby tool means in order to facilitate the removal by extraction.

In the form of the plug shown in FIG. 9 the cross-sectional shape of thestrip material is modified and provides a step forming rib 34 on thewider edge portion of the strip material and the edge adapted to bedirected towards the wide end of the plug member 10.

In the modification shown in FIG. 10 a outwardly protruding lip 36 isprovided at the narrow edge of the tapering section strip materialdirected towards the small end of the plug member.

Plug members according to the invention may be manufactured by injectionmoulding between coacting complementary male and female moulds. In oneform an open radially widening pitched spiral strip is moulded on aplane with major faces of the strip slopingly relative to the plane. Thespiral strip is subsequently drawn to form the truncated cone-shapedmember with the major faces of the convolutions of the thus formed helixconverging toward the wide end of the member. In another form ofmoulding coacting moulds present continuous rebatelike spiral recesses.After moulding of the strip material and removal from the moulds thesmall end of the thus formed helical spiral is displaced in an axialdirection through the larger end and whereby the convolutions becomeplaced in their required overlapping positions with the major facesconverging toward the wide end of the truncated cone member thus formed.

Alternatively the strip material may be formed in a plane and accordingto a substantially rapidly widening s iral. Such spiral, of which thecross section of the strip material is also of tapering shape, can bemanufactured by injection moulding. Such widening spiral may besubsequently wound to the required frustoconically shaped helicallycoiled plug member.

The outwardly directed face of the large end convolution is preferablyroughened or provided with protrusions for increased nonslippingengagement with the surface of the hole in which it is placed.

The plug member according to the invention is particularly intended foruse as a tamping plug to contain the gasses of combustion and explosionin a blast hole. The plug member may also be used for other purposessuch as for instance, as a socket plug for placement in sockets left inrock which have previously being drilled and blasted. The plug memberaccording to the invention may also be used as a wedging device tosecure a bolt placed in drilled holes for the anchoring of roof bolts orthe like.

The cross-sectional shape of the strip material may vary in respect ofat least portions of its length.

lclaim:

l. A tapering tubular plug member having a wide end and a small end andcomprising a helically wound strip of material presenting a pair ofopposed wide faces, the helically wound strip material providingoverlapping convolutions of progressively smaller size and whichconvolutions are arranged with both the wide faces of the strip materialconvergent toward the wide end of the member and with smallerconvolutions extending from the larger convolutions, within which theyare disposed, in the direction of the small end of the member whereby,on application of a force in a substantially axial direction on thesmall end of the member and toward the wide end of the member, the widefaces of the helically wound strip slide and engage wedgingly on oneanother and cause radial expansion of the convolutions for theconvolution at the wide end of the member to tightly engage onto wallsof a hole in which the member is located.

2. A tapering tubular plug member as claimed in claim 1 wherein thestrip material is of narrow rectangular cross-sectional shape.

3. A plug member as claimed in claim 1 wherein the strip material is oftapering and substantially truncated narrow triangular cross-sectionalshape, the wide and relatively sloping faces of the helically woundstrip material being arranged to converge in the direction of the wideend of the member and diverge in the direction of the small end of themember.

4. A tapering tubular plug member as claimed in claim 1 wherein thestrip material provides a transverse end portion disposed across thesmall end of the member.

5. A tapering tubular plug member as claimed in claim 1 wherein theportion of the strip material adapted to form the convolution at thewide end of the member is of progressively decreased thickness andadapted to form a substantially true cylindrical circumferential facefor engaging the walls of the hole, said true cylindrical surfacebeingsurmounted by a generally conical surface of substantiallyhelically ribbed appearance presented by exposed portions of theoverlapping convolutions of the helically wound strip material.

6. A tapering tubular plug member as claimed in claim 1 wherein asubstantially conical part is provided on the end of the strip at thesmall end of the member, said conical part being provided with an axialpassage and is arranged with its small end directed toward the wide endof the member.

7. A tapering tubular plug member as claimed in claim 1 wherein anoutwardly flared formation is provided on an outwardly directed edgeportion of the convolution at the small end of the member.

8. A tapering tubular plug member as claimed in claim 1 wherein aformation for engagement by tool means, for extraction of the member, isprovided on a portion of the inwardly directed wide face of theconvolution at the wide end of the member.

9. A tapering tubular plug member as claimed in claim 1 wherein thestrip material is provided at an edge portion, to be directed toward thewide end of the member, with a lip which is directed inwardly of themember.

10. A tapering tubular plug member as claimed in claim 1 wherein thestrip material is provided at an edge portion, to be directed toward thesmall end of the member, with a lip directed outwardly of the member.

1. A tapering tubular plug member having a wide end and a small end andcomprising a helically wound strip of material presenting a pair ofopposed wide faces, the helically wound strip material providingoverlapping convolutions of progressively smaller size and whichconvolutions are arranged with both the wide faces of the strip materialconvergent toward the wide end of the member and with smallerconvolutions extending from the larger convolutions, within which theyare disposed, in the direction of the small end of the member whereby,on application of a force in a substantially axial direction on thesmall end of the member and toward the wide end of the member, the widefaces of the helically wound strip slide and engage wedgingly on oneanother and cause radial expansion of the convolutions for theconvolution at the wide end of the member to tightly engage onto wallsof a hole in which the member is located.
 2. A tapering tubular plugmember as claimed in claim 1 wherein the strip material is of narrowrectangular cross-sectional shape.
 3. A plug member as claimed in claim1 wherein the strip material is of tapering and substantially truncatednarrow triangular cross-sectional shape, the wide and relatively slopingfaces of the helically wound strip material being arranged to convergein the direction of the wide end of the member and diverge in thedirection of the small end of the member.
 4. A tapering tubular plugmember as claimed in claim 1 wherein the strip material provides atransverse end portion disposed across the small end of the member.
 5. Atapering tubular plug member as claimed in claim 1 wherein the portionof the strip material adapted to form the convolution at the wide end ofthe member is of progressively decreased thickness and adapted to form asubstantially true cylindrical circumferential face for engaging thewalls of the hole, said true cylindrical surface being surmounted by agenerally conical surface of substantially helically ribbed appearancepresented by exposed portions of the overlapping convolutions of thehelically wound strip material.
 6. A tapering tubular plug member asclaimed in claim 1 wherein a substantially conical part is provided onthe end of the strip at the small end of the member, said conical partbeing provided with an axial passage and is arranged with its small enddirected toward the wide end of the member.
 7. A tapering tubular plugmember as claimed in claim 1 wherein an outwardly flared formation isprovided on an outwardly directed edge portion of the convolution at thesmall end of the member.
 8. A tapering tubular plug member as claimed Inclaim 1 wherein a formation for engagement by tool means, for extractionof the member, is provided on a portion of the inwardly directed wideface of the convolution at the wide end of the member.
 9. A taperingtubular plug member as claimed in claim 1 wherein the strip material isprovided at an edge portion, to be directed toward the wide end of themember, with a lip which is directed inwardly of the member.
 10. Atapering tubular plug member as claimed in claim 1 wherein the stripmaterial is provided at an edge portion, to be directed toward the smallend of the member, with a lip directed outwardly of the member.